The transverse flow of entropy in solids and electronic topology

In the semiclassical picture of thermal and thermoelectric transport, heat-carrying quasi-particles such as electrons and phonons are scattered after traveling a finite distance. The two signatures of this picture are the Wiedemann-Franz law and Mott’s formula. The first part of this talk reviews our present picture of transverse thermoelectricity (Nernst) and transverse thermal (Righi-Leduc or thermal Hall) effects, with a focus on the extreme variety of the magnitude of the Nernst coefficient in metals explained by the semiclassical picture.

The second part of the talk is devoted to non-trivial electronic topology. The thermoelectric and thermal counterparts of the anomalous Hall effect arise because of the Berry curvature of electrons when the host solid lacks time-reversal symmetry. Our ongoing research aims to measure and to understand the transverse thermoelectric and thermal responses caused by the ‘anomalous velocity’ of electrons in magnetically-ordered solids.